Porceddu Riccardo, Porcu Cristina, Mulas Giovanna, Spiga Saturnino, Follesa Maria Cristina
Sezione di Biologia Animale ed Ecologia, Dipartimento di Scienze della Vita e dell'Ambiente, Università degli Studi di Cagliari, Cagliari, Italy.
CoNISMa Consorzio Nazionale Interuniversitario per le Scienze Mare, Rome, Italy.
Front Neuroanat. 2024 Jan 4;17:1301651. doi: 10.3389/fnana.2023.1301651. eCollection 2023.
The catecholaminergic component of the brain-pituitary-gonadal axis, which mediates the influence of external and internal stimuli on the central nervous system and gonad development in vertebrates, is largely unexplored in Chondrichthyes. We considered (L., 1758) females as a model for this vertebrate's class, to assess the involvement of the catecholaminergic system of the brain in its reproduction. Along the reproductive cycle, we characterized and evaluated differences in somata morphometry and the number of putative catecholaminergic neurons in two brain nuclei: the periventricular preoptic nucleus, hypothesized to be a positive control for ovarian development, and the suprachiasmatic nucleus, examined as a negative control.
16 wild females were sampled and grouped in maturity stages (immature, maturing, mature, and mature egg-laying). The ovary was histologically processed for the qualitative description of maturity stages. Anti-tyrosine hydroxylase immunofluorescence was performed on the diencephalic brain sections. The immunoreactive somata were investigated for morphometry and counted using the optical fractionator method, throughout the confocal microscopy.
Qualitative and quantitative research confirmed two separate populations of immunoreactive neurons. The modifications detected in the preoptic nucleus revealed that somata were more numerous, significantly smaller in size, and more excitable during the maturing phase but decreased, becoming slightly bigger and less excitable in the egg-laying stage. This may indicate that the catecholaminergic preoptic nucleus is involved in the control of reproduction, regulating both the onset of puberty and the imminent spawning. In contrast, somata in the suprachiasmatic nucleus grew in size and underwent turnover in morphometry, increasing the total number from the immature-virgin to maturing stage, with similar values in the more advanced maturity stages. These changes were not linked to a reproductive role. These findings provide new valuable information on Chondrichthyes, suggesting the existence of an additional brain system implicated in the integration of internal and environmental cues for reproduction.
脑-垂体-性腺轴的儿茶酚胺能成分介导了外部和内部刺激对脊椎动物中枢神经系统和性腺发育的影响，在软骨鱼类中这方面的研究基本尚未开展。我们将（L.，1758）雌性个体作为该脊椎动物类群的模型，以评估脑内儿茶酚胺能系统在其繁殖过程中的作用。在整个生殖周期中，我们对两个脑核中体细胞形态测量和假定的儿茶酚胺能神经元数量的差异进行了表征和评估：室周视前核，被假定为卵巢发育的阳性对照；以及视交叉上核，作为阴性对照进行研究。
采集了16只野生雌性个体，并根据成熟阶段（未成熟、成熟中、成熟、成熟产卵）进行分组。对卵巢进行组织学处理，以定性描述成熟阶段。对间脑脑切片进行抗酪氨酸羟化酶免疫荧光检测。通过共聚焦显微镜，使用光学分割法对免疫反应性体细胞进行形态测量和计数。
定性和定量研究证实了两个不同的免疫反应性神经元群体。视前核中检测到的变化表明，在成熟阶段体细胞数量更多、尺寸明显更小且更易兴奋，但在产卵阶段数量减少，变得稍大且兴奋性降低。这可能表明儿茶酚胺能视前核参与了繁殖控制，调节青春期的开始和即将到来的产卵。相比之下，视交叉上核中的体细胞尺寸增大且形态测量发生变化，从未成熟处女阶段到成熟中阶段总数增加，在更高级的成熟阶段数值相似。这些变化与生殖作用无关。这些发现为软骨鱼类提供了新的有价值信息，表明存在一个额外的脑系统，参与整合内部和环境线索以进行繁殖。
